At a White House press conference Wednesday, Mr. Bush acknowledged that the United States had no proof that top Iranian leaders such as President Mahmoud Ahmadinejad had approved the shipment of the explosively formed penetrators. But he said that US intelligence was convinced that the Al Qods force of Iran's Revolutionary Guard was the source of the weapons.

"What's worse? That the [Iranian government] knew? Or that it didn't know?" said Bush.

The press conference was the first Bush has held since Dec. 20. It came as the House of Representatives debated a nonbinding resolution of disapproval of his decision to send 21,500 additional troops to Iraq.

Bush said he was under no illusion as to the outcome of the vote, and that he knew some Republicans would join Democrats in voting against the plan.

He warned lawmakers, however, that he would oppose strenuously any attempt at legislation cutting off funds for the troop increase.

"My hope is that this nonbinding resolution does not turn into a binding policy that tries to prevent people from trying to do what I've asked them to do," said Bush.

He began with a lengthy statement about his Iraq plan, insisting that success there will help secure the American homeland. The government of Iraqi Prime Minister Nouri al-Maliki has specific benchmarks it must hit as part of the plan, said the US president, and it is making progress in doing so.

The Iraqis have passed a budget that includes $10 billion for reconstruction, as called for by the plan, said Bush. It is also in the process of making final a law that would allocate oil money as equally as possible among Iraqi population groups.

"I'm paying close attention to whether or not [Iraq] is meeting these benchmarks," said Bush.

He also defended the deal on North Korea's nuclear program that was reached earlier this week. Critics on the left have said the deal, under which Pyongyang will receive energy aid in return for shutting down its main nuclear reactor, is one that could have been reached earlier. Critics on the right, such as Bush's former UN ambassador, John Bolton, have said the deal is a sellout that would allow the North Koreans to retain any fissionable material they have already produced.

"I strongly disagree with [Bolton's] assessment," said Bush. "Like the Iranian issue, I wanted to resolve the North Korean issue peacefully."

Though most of the questions from the press dealt with international problems, the president did get a few queries on domestic issues. He said that he still hoped to work with Democrats in Congress on such issues as immigration and education, but he declined to say anything about the trial of I. Lewis "Scooter" Libby, Vice President Dick Cheney's former chief of staff, on perjury charges.

He also laid down what he jokingly called a "marker" for reporters present, saying he would have no comment on the race to be his replacement.

"I will resist all temptation to become the pundit in chief," said Bush.